1. Field of the Invention
This invention relates to an improved pressure and vacuum relief safety valve having a movable diaphragm, and more particularly to a safety valve having means for removing condensate from a control chamber.
2. Description of the Prior Art
Relief valves are widely employed throughout many industries to relieve the pressure in containers such as storage tanks, boilers and pipelines to prevent damage to these containers due to excessive pressures or to excessive vacuums. Some of the simplier relief valves employ a spring to bias a diaphragm over an opening to retain gas or fluid in the container until the inside pressure reaches a predetermined value, then allow the diaphragm to move away from the opening to relieve the excessive pressure or the excessive vacuum. More accurate control of the inside pressure can be obtained by using a relief valve without a spring and employing one or more pilot valves to control the opening and closing of the diaphragm. Such a combination is disclosed in U.S. Pat. No. 3,592,224, issued to L. Bois on July 13, 1971. A device of this type affords many advantages, especially opening and closing of the valves corresponding to very precise pressure valves which may be very close to the predetermined opening value, and such devices also work quite well while the storage temperature is nearer the ambient temperature. However, when the storage temperature is above the ambient temperature, condensates may form in a pressure control chamber of the relief valve, and these condensates may interfere with the operation of the valve. Accordingly, what is needed is a device for removing the condensate from the pressure control chamber, and for either returning the condensate to the storage container or venting the condensate to the atmosphere.